A new inhibitor of human secretory phospholipase A2 (PLA2), cacospongionolide E (4a), has been isolated from the Tyrrhenian sponge Fasciospongia cavernosa. The structure was proposed on the basis of spectroscopic data and by chemical transformations. The absolute configuration of cacospongionolides 2a-4a was established using the modified Mosher's method. Cacospongionolide E was the most potent inhibitor toward human synovial PLA2, showing higher potency than the reference compound manoalide and exerting no signs of toxicity on human neutrophils. It showed high activity in the Artemia salina bioassay and moderate toxicity in the fish (Gambusia affinis) lethality assay.

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Our results indicate that inhibition of 5-LO could participate in the anti-inflammatory properties of this natural product.